A transmissive or transflective liquid crystal display device includes a liquid crystal display panel and an illuminating device (a so-called backlight) disposed behind the liquid crystal display panel. In this type of liquid crystal display device, planar light emitted from the illuminating device is used to display an image on a display screen of the liquid crystal display panel.
An edge (side) light type illuminating device is known as the illuminating device, which has a configuration that light-emitting boards such as LED (Light Emitting Diode) boards, which include long wiring boards on which a plurality of LEDs (Light Emitting Diodes) are aligned, are disposed along end faces of a light guide plate that defines a clear plate made from an acrylate resin. In this type of illuminating device, the light emitted from the light-emitting boards is guided to enter the light guide plate from the end faces of the light guide plate, and thereby the entering light is made into planar light and emitted from a front face of the light guide plate. The light guide plate includes scattering members in a dot pattern that are disposed over a back face or a front face of the light guide plate and arranged to scatter the light that enters from the end faces of the light guide plate. In addition, a reflection sheet arranged to reflect the light is provided on the back face of the light guide plate. Thus, the light emitted from the light-emitting boards as described above is scattered or reflected by the scattering members or the reflection sheet, and is thus made into planar light and emitted from the front face of the light guide plate.
The positions at which the light-emitting boards are disposed in this illuminating device are determined considering brightness required of the illuminating device, brightness required of the light-emitting boards, and size required of the light guide plate (the liquid crystal display panel). For example, when a light guide plate is relatively small in size, LED boards disposed along one end face of a light guide plate can provide enough brightness as is disclosed in the illuminating device of PTL 1 (JP 2006-310221). Meanwhile, when a light guide plate is relatively large in size, a plurality of light-emitting boards are disposed along a plurality of end faces of a light guide plate in order to provide enough brightness in a convincing way.
In an illuminating device used in a large liquid crystal display device, a plurality of LED boards are sometimes aligned on one end face of a light guide plate. For example, when the plurality of LED boards are connected in series as one LED board, a voltage placed on the LED board becomes too large. For this reason, the plurality of LED boards that are separated from each other are aligned horizontally on one end face of the light guide plate as described above.
FIG. 7 is a plan view showing a schematic configuration of a conventional illuminating device 1P. The illuminating device 1P mainly includes a backlight chassis 4P having a box shape, a light guide plate 7P having a rectangular shaped and housed in the backlight chassis 4P, and a plurality of (four) LED boards 5P including long wiring boards 52P on which a plurality of LEDs 51P are mounted. The LED boards 5P are of the same kind, and are same in length (the lengths of the long wiring boards 52P are same). Two LED boards 5P are aligned along an end face 71P on one long side of the light guide plate 7P, and two LED boards 5P are aligned along an end face 71P on the other long side as shown in FIG. 7. The LED boards 5P along the end faces 71P face each other sandwiching the light guide plate 7P therebetween. Clearances 53P are each formed between the adjacent LED boards 5P along the end faces 71P. The clearances 53P are disposed so as to face each other.
PTL 2 (JP 2009-37212) discloses a technique relating to the present invention.